Study On Ecological Effects Of Two Amaranth Invasive Plants On The Functional Traits Of Native Plants

Exotic plant invasion may have unique functional traits that distinguish them from other species.Comparing the differences in functional traits between invasive and native plants is an important research method to reveal the trait advantages in invasive biology.In addition,the impact of invasive plants on native community structure and environmental factors may be different under different invasive pressures and habitats.Therefore,in this study,Amaranthus retroflexus and its native coexisting plants were taken as the research objects under different invasion pressures,Amaranthus palmeri and its native coexisting plants were taken as the research objects under different habitats to study the differences of functional traits between invasive plants and native plants,and the influence of invasion on soil factors.Besides,the differences of plant functional traits in response to soil factors were explored,key functional traits and soil factors were selected,so as to accurately reveal the invasion mechanism of Amaranthus retroflexus and Amaranthus palmeri,provide theoretical reference for the prevention and control of invasive plants represented by amaranth.The main conclusions are as follows:(1)The effects of A.retroflexus on native plant species,plant numbers,biomass,leaf functional traits and soil factors under different invasion pressures were analyzed.The results showed that the number of native plants,plant numbers and above-ground dry weight gradually decreased with the invasion of A.retroflexus;Under the severe invasion pressure,nitrogen content of A.retroflexus was significantly increased,while carbon content,C/ N ratio,and leaf construction cost were significantly decreased,and no significant change of specific leaf area.Native species had lower carbon content and C/ N,and higher SLA.Under the mild invasion pressure,there were no significant differences in of all examined traits between A.retroflexus and the native species.The invasion of A.retroflexus increased soil total nitrogen content and ratio of nitrogen and phosphorus significantly under low invasion pressure compared to no invasion pressure(P<0.05).But soil carbon to nitrogen ratio was significantly decreased(P<0.05).There were no significant differences in soil total carbon,total phosphorus,and carbon to phosphorus ratio under different invasion pressures.Our results suggested that higher resource utilization efficiency、lower resource capture costs and change of the soil environment were the main reasons responsible for the successful invasion of A.retroflexus.A redundancy analysis indicates: The dominant factor of native plants under no invasion pressure is soil total phosphorus content;under low invasion pressure,soil total nitrogen content is the main influencing factor of native plants,while A.retroflexus is greatly affected by soil carbon to phosphorus ratio;under severe invasion pressure,the dominant factor of native plants and A.retroflexus are the content of soil total nitrogen content,but SN mainly affects the leaf construction cost and leaf area of A.retroflexus which is different from the environmental adaptation strategy of native plants.(2)The effects of Amaranthus palmeri invasion on the functional traits and soil factors of native plant in different habitats indicates that: most traits of A.palmeri were significantly different from native plant in the same habitat;compared with native plant,A.palmeri had a greater response to environmental heterogeneity and higher phenotypic plasticity.the soil water content of both species shows a significant difference(P<0.05)with maximum in riverbank habitat to lowest in roadside habitat.Soil N/P ratio,C/N ratio,and C/P ratio of rb habitats are significantly lower compared to wl and rs habitats(P<0.05).The results indicate that invasive plant had a higher phenotypic plasticity and had different response and adaptability to the environment than native plant.A redundancy analysis between functional traits and soil factors of A.palmeri and native plant indicates: that soil water content is the dominant soil factor affecting the functional traits of A.palmeri and native plant.However,A.palmeri forms an environmental adaptation strategy by changing traits of SDW,LN,and leaf C/N ratio,which is different from native plant by changing traits of LA and LDW.